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Contacts Test 4

Light refracts first through the contact lens and then through the ____________? lacrimal lens
How is the lacrimal lens formed? The tears collected between the back of the CL and the front of the eye.
The spectacle Rx is a combination of the....? Contact lens power + lacrimal lens power
What is the lacrimal lens equal to...? The difference between the Ks
What is the first thing to do when finding the power? Put the spectacle Rx in minus cylinder form
When do you compensate for vertex distance in contact fitting? When the prescription is 4.00 D or greater
What does SAM stand for? Steeper Adds Minus
What does FAP stand for? Flatter Add Plus
What is the first thing you do to find the base curve? Determine the flat K
What are the three different ways to fit contacts? On K, steeper than K (STK), flatter than K (FTK)
When fitting flatter or steeper than K what power is corrected? Only the sphere power
When fitting flatter or steeper than K, you are accommodating for the _____, and the effective sphere power....? accommodating for the tears; effective spherical power stays the same
What is residual astigmatism? difference between the refracted astigmatism and corneal astigmatism
What causes residual astigmatism? internal or lenticular astigmatism
How is residual astigmatism found? refracted astigmatism - corneal astigmatism = residual astigmatism
Anytime corneal astigmatism is greater, the residual will be a plus or minus? plus
For every 0.25D change in K's the radius of curvature changes approximately ____ mm? 0.05
For every 0.50D change in K's the radius of curvature changes approximately ___ mm? 0.10
How are rigid lenses packaged? dry in a flat pack
How are the lenses cleaned? with 2-4 drops of Boston cleaner; using pinky rub from center to the outer edge (not in circles) flip over, clean the other side; hold lens and rinse with saline or water; pat dry
If lenses are being dispensed to the patient they are stored in...? Boston conditioning
What is verified and inspected on the rigid lenses? Base curve; power; diameter; POZ width; PPC width; bifocal seg height; center thickness; blends; edge contour; surface quality
What is used to verify base curve? radiuscope; radius gauge; microspherometer; contactoguage; attachment to keratometer (con-ta-check)
What are two other names for the base curve? radius of curvature; central posterior curve
What is used to measure the power of the lens? Lensometer (vertometer; focimeter; lensmeter)
What is BVP? Back vertex power
What is FVP? front vertex power
When measuring BVP, what side of the lens is towards the lens stop? concave side
When measuring FVP, what side of the lens is towards the lens stop? convex side
Which side will measure more plus, BVP or FVP? BVP
What is used to measure diameter? diameter gauge (slot gauge, v-groove); measuring magnifier (monocular magnifier, measuring loupe); shadowgraph (projection magnifier)
What is used to measure the posterior optical zone width? measuring magnifier and shadowgraph
What is used to measure the posterior peripheral curve width? measuring magnifier and shadowgraph; if you have a light blend you can measure PPC and PIC; if you have med or heavy blend, you won't be able to tell the difference
What is used to measure the bifocal seg height? measuring magnifier and shadowgraph
Where is the seg height measured? from the truncated part of the lens to the top of the seg
What is the center thickness measured with? Thickness gauge (dial gauge); attachment to the radiuscope
What is used to inspect and analyze the blends? profile analyzer and fluorescent light (fluorescent tube).
What are you looking for when inspecting the blends? The reflection of light on the lens to make a J or ski-edge
When using the fluorescent light to inspect the blends the light must be where in relation to the examiner? in front of and higher than the examiner
What is used to check the edge contour and finish? measuring magnifier; shadowgraph; lens on finger using slit lamp
What are you looking for when checking edge contour? Edge shouldn't be too thick or too thin, and should be smooth and clear
What is used to check the surface quality of the lens? Measuring magnifier; shadowgraph; slit lamp
What are you looking for when checking the surface quality? nice clear lens with no lathe marks or scratches
What does an orange peel effect mean when inspecting surface quality? The lens was not polished enough
What does a black dot on a lens mean? Right eye
What is fenestration? a hole (or many holes) in the lens to get more oxygen
What does ANSI stand for? American National Standards Institute
What is ANSI? A non-governmental, national organization that has standards that are recommendations not requirements
The ANSI standards are a guideline, and your standards can be ________? stricter
If you don't receive what is ordered what should you do? Send it back
What order should you use when verifying and ordering lenses? Base Curve; Power; Diameter; OZ, CT
ANSI standards for Base Curve? +(-)0.05
ANSI standards for power 0.00 to 5.00 D +(-)0.12
ANSI standards for power 5.12 to 10.00 D +(-)0.18
ANSI standards for power 10.12 to 15.00 D +(-)0.25
ANSI standards for power 15.12 to 20.00 D +(-)0.37
ANSI standards for power over 20.00 D +(-)0.50
ANSI standards for Diameter +(-)0.05
ANSI standards for Posterior Optical Zone +(-)0.10
ANSI standards for Center Thickness +(-)0.02
Created by: griffiskr